Embodiments of the invention relate generally to rotary pull switches and, more particularly, to contactless rotary pull switches such as might be used as lighting switches for a motor vehicle.
In specialty vehicle markets—such as heavy trucks, agricultural equipment, and construction equipment, for example—various types of electrical switches are used as control switches for a variety of applications, including general vehicle features/applications (e.g., switching the motor vehicle lighting, the windshield wipers, the rear windshield heating, the cruise control functions, etc., on and off) and critical or safety related vehicle features/applications (e.g., power take-off (PTO) switches, “e-stop” type switches, etc.). With respect to a vehicle lighting switch in particular, a typical vehicle lighting switch includes a rotary control having at least three positions: all lights (parking lamps and headlamps) OFF, parking lamps ON, and all lights ON. The vehicle lighting switch may also incorporate an auto-light function, and two pull-on functions for turning ON fog lamps.
The typical rotary pull vehicle lighting switch includes mechanically engageable contacts (e.g., wiping contacts) for controlling all of the vehicle lighting functions/modes—with a sensing or determination of a rotational position and pull position being achieved via such mechanically engageable contacts. While such rotary pull switches having mechanically engageable contacts are most often employed in vehicle lighting switches, it is recognized that vehicle lighting switches may also be constructed as contactless rotary pull switches. Such contactless rotary pull switches may operate by rotating a magnet past a fixed magnetic sensor, such as a Hall effect IC or a magnetoresistive sensor. It is also known to make a contactless switch that operates using the Wiegand effect.
With respect to contactless rotary pull switches that are utilized in vehicle lighting switches or in switches for other applications, it is recognized that existing designs of such switches can limit the performance thereof. For example, existing contactless rotary pull switches often incorporate a single magnet or arrangement of magnets—in conjunction with a number of sensors—for determining both the rotational position of the switch and the pull position of the switch. In such an arrangement, the pull position is determined by sensing the strength of a magnetic field of the magnet by way of a pull position sensor—with the strength of the magnetic field varying as a distance between the magnet and the pull position sensor increases/decreases. However, these variations in the magnetic field strength may not be great enough to discern a distinct switching position. As another example of limited performance, the circuit board in existing contactless rotary pull switches—and light emitting diodes (LEDs) included on the circuit board for providing backlighting to symbols on the face of the switch—are often located at a back portion of the switch module at a distance from the vehicle dashboard. As such, mechanisms such as optical fibers or light pipes are necessary for transmitting light from the LEDs to the symbols on the face of the switch, thereby increasing the cost and complexity of the switch.
It would therefore be desirable to provide a contactless rotary pull switch—such as might be utilized for controlling of vehicle lighting—that provides distinct switching positions and increased durability. It would further be desirable for such a rotary pull switch to utilize low cost and efficient lighting to provide backlighting for lighted symbols on the face of the switch.